Dental flask



N. OPOTOW DENTAL FLASK Aug. 31, 1948-.

Filed NOV. 13, 1946 Patented Aug. 31, 1948 UNITED STATES PATENT OFFICE DENTAL FLASK Nathan Opotow, New York, N. Y. Application November 13, 1946, Serial No. 709,566

6 Claims. 1

This invention relates to dental flasks used by dentists and dental technicians for forming partial or full artificial dentures.

The present application is a continuation in part of my application Serial No. 634,735, filed December 13, 1945, now Patent No. 2,440,910.

As recited in the above mentioned patent application, artificial dentures are usually made by investing an upper or lower model of the jaw structure into the lower portion orsection of a dental flask together with the waxed-up case representing a prototype of the finisheddenture.

'The surface of the plaster which invests the model is then. coated with oil or soap and the upper section of the flask is thereafter applied over the lower section and filled with plaster or artificial stone or any other suitable component serving. as investin material. The cover is then applied and the material is allowed to set. Thereafter, the assembled flask is immersed in boiling water for several minutes, whereupon the upper section of theflask is separated from the lower section, The wax of the waxed-up case is now washed or flushed out. it having been melted or softenedduring the boiling process; 'A thermoplastic material, such as various acrylates, or any other suitable denture material, is then applied to the .space left by. the wax, and the upper portion of. the flask is restored. The reassembled flask is then subjected to pressure in order to distribute the plastic material. properly. The flask is ordinarily re-opened thereafter and more material is added until. when pressure is reapplied, the surplus material within the flask is forced through the line where meet. The. flask is again opened and all excess material from the investment portion is. removed, but not fromthe denture. Then theflask is sub jected to considerable pressure to force out any excess of material over the denture .until the flask isvproperly closed so as to maintain the original plan of the dentur The flask is, now processed by heat, to curethe denture. material. It is awell known fact thatupon curing, the volume of the, denture. material decreases considerably. Consequently, the accuracy of the fin:- ished denture suifers. In fact, some techniques utilize an over-supply of, material which maintains the flask slightly open even when under pressure. Inv such techniques, thesurplus material is expected to compensate for curing shrinkage. However, it is practically impossible to both gaugethe amount of curing shrinkage actually so as to predetermine the degree of over-supply and to determine Where, in the various regions the flaskhalves of the denture, the surplus should be applied. Furthermore, it is to be observed that a function of the excess is to apply pressure to the material whereas, if the eXcess becomes substitutedfor the shrunken material, a proportional pressure loss-is encountered. A solution often practiced is to apply a great excess of material, but this merely opens the flask more anddecreases the accuracy of the finished denture. In, addition, a method known as injection molding is often practiced but whereas it is possible to continue the supply of material as necessary under this method, it is extremely difficult. to achieve a proper distribution of theadded material.

Thus, theabove known methods, while generally practiced throughout the industry, involve many difficulties and are productive of unsatisfactory results in a large percentage of cases. In general, the principal objection is the production of discrepancies between the wax pattern and the cured denture through alteration of the planned occlusion.

It is further noted that a method, sometimes referred to as a banking procedure, has been practiced but only for small, partial dentures. This method avoids the necessity of separating the teeth and model after the wax has been washed away. It is accomplished by investing the teeth and model in one half of the flask, while baking the plaster around the teeth and model far above the height of theflask portion in which it is invested. The upper portion is formed with a mound of plaster in the form of a plunger, the wax is eliminated as previously, and the denture material is applied through the lingual side of the case. This method permits a suflicient or even a highly excess supply of plastic denture material to compensate for the curing shrinkage and to assure proper compression.

Processing of the artificial denture by the banking method above described has not been generally adopted in spite of its benefits because of other difliculties which have made its use impractical in many cases. Thus, the banking procedure may be employed where small partial dentures are required, but it is rarely or never employed where an extensive partial or a full denture is to be prepared. The principal difliculty has been the fact that the application of pressure to force the plastic material into place and to insure proper compression thereof, very often cracks the banked wall of plaster and virtually destroys the denture. In my application described above, I disclosed a substantially threepiece dental flask wherein a banking process cation from a three-piece to a two-piece construction so as to eliminate as far as possible undesired displacement between the flask sections and insure accuracy throughout th procedure, although high pressure maybe used as required.

Other objects of my invention will be apparent from the following description, it being understood that the above generalstatements of the objects of my. invention are intended to describe and not limit it in any manner.

Referring to the drawing:

Fig. 1 is a perspective view section Fig. 2 isa perspective view of the lower flask section.-

Fig, 3 is a rear elevational; view of. this flask, shownpartly broken away-toillustrate the floor knockout block thereof.

The flask comprises the lowersection or receptaclelflhaving aconventional knockout block Illa to facilitate removal of the finished denture. Receptacle l isformed with a surrounding wall I l. Lugsor pins-l2 formed on the upper surface of receptacle lil complement the openings l3 and M of flask upper-section I5.

Section I5 is formedwith'a ceiling l6 and a depending wall H which though considerably smaller than wall I l, is nevertheless of such a size as to embrace a mound of plaster as will-be hereinafter described. Upper section=l6 is formed with an off-set member in the form-of depending flange, l8 which fits into. an appropriate cutout it! of the top. flask of receptacle [0. Thus, referringtov Fig; 3, when the upper and lower flask sections are assembled, the flaskassumes its closed position whereby pressure may be applied tov the-contents aspabove described.

- Inorder to utilizetheimproved dental flask, the teeth in the form-of a waxed-up case and the model of the jaw structure-are invested in the receptacle It The investment while in thereceptacle is then coated with oil, soap-or any other separating material, and more plaster is-applied thereover. Then'the uppersection I5 is applied in position. After setting, the plasterlast applied is retained-by the upper section IS, the openings and 2! of which function as gripping means for the set plaster. Whenthe section l5'with the set plaster thereon is withdrawn, the-plaster is in-the shape of a'mound which functionsas a plunger for compressing the artificial. denture". material thereafter applied, Indentations 22 and 23 in the upper section 15 are provided. to facilitate separation of the flask sections by anappropriate tool.

When the upper section l5 and the plaster-filled fiaskenclosingthe model-and waxedeup case are assembled, and the plaster has set, the flask is heated so as to boil out thewaxwhichheld the artificial teeth. Theseteeth will now be retained in the plaster of the receptacle [0 so that the flask may be separated without altering their position.

The. wax having been boiled away, the teeth will l press.

be separated from the model gum ridge which will likewise be retained in its original position. Cutout or opening 59 then serves the function of a window through the upper, rear area of wall H by which the teeth can be seen and cleaned of foreign material. Furthermore, the denture material may be applied through th cutout l9 since the teeth and model gum ridge are fully accessible both visually and physically from a rear lateral portion ofIth-e lower flasksection. It will be noted that'front-wall portion I la surrounds and protects the set plaster material adjacent the teeth so as to protect the case against fracture when the upper member He is thereafter applied with pressure. Inasmuch as the teeth and model can have noirelative movement after the investment, a sufficient quantity of. dental material to compensate for curing shrinkage can be applied without risking any change in the cured denture.

The upper section, having the set plaster mound thereon heldbythe openings wand 2! and by the depending. wall H, is restored to. the complementary lower section. The wall l'Lwhich surrounds theuppersection and nests in the cutout lfl may be about inch inheight to embrace a portion of the -mound. The assemblage is then subjectedtopressure in. a bench press whereupon the. mound compresses the. plasticdenture material so that it fillsthe space left .bythe boiled out wax. The .degreeeof compression. can be very great, if desired, without fracturing. the plaster investmentsince the wallsection Ha provides a flrm backing fortheteeth and plaster behind it. The applicationof a considerable over-supply of denture material ;-is made possible. to assure sufficient compression and density Without altering the lanned. occlusion.

After initial, pressure, the flask may be reopened for the application of further denture material to insure against a possible deficiency. Suchre-opening, of. course, .cannot affect the occlusion because the-teeth remainflxed in th lowersection. Alcompensating spring press is thereafter .appliedtothe assembled flask which is then boiledfora conventionalperiod of time, approximately one hour,. depending upon the. material used. The spring press is then taken off and the finished denture .is removed in the usual manner. It has-been foundthat withthe three-piece constructionof my former application, the intermediate piece-would sometimes separate slightly fromthelower section dueboth tothe resiliency of theplastic material in .the bench press and to its .tendency to expand whencuring in the spring Such. a separation, in some instances, might crack .the plaster although, in the majorit of .instances, thisdid not-occur. In the present constructiomhowever, this. is avoided because of the. unitary. or integral. nature of the lower section.

It will be apparentthat the improved dental flask can also be utilized for investment procedureswherein the artificial teeth are retained in the removed section, if this procedure is desired.

It may be noted that, in the instant application, the depending flange I3 is a portion of the upper section .l5'so as to back up themound formed on the section l5 and enhanceits retention thereon. The wall l1 cooperates with the flange [8 in this respect. Section l5, although being a distinct flask section, is also a cover or closure member for the flask indistinction to the usual, substantially flat plate used forthis purpose.

I haveshowna preferred embodiment of my invention,. but it is. obvious that. numerous changes and omissions may be made therefrom without departing from its spirit.

I claim:

1. A dental flask comprising a pair of complementary upper and lower sections, said lower section having a surrounding wall and an opening formed in a rear portion thereof adapted to permit lateral access to the interior of said lower section, and an offset member integral with said upper section for covering said opening when said upper and lower sections are assembled, and plaster retaining means on said upper section so as to retain a mound of set plaster by embracing a portion thereof, said upper section serving as a cover for the flask.

2. A dental flask comprising a pair of complementar upper and lower sections, said lower section having a surrounding wall and having an area thereof cut away to define an opening so as to permit lateral access to the interior of the lower section, and a depending member on said upper section formed so as to nest in said area and to substantially close said opening when the flask is assembled, said upper section being of a depth to maintain a mound of set plaster therein whereby said mound may be forced into said lower section when the flask is assembled and pressure is applied thereagainst, said upper section serving as a cover for the flask.

3. A dental flask comprising a pair of complementary upper and lower sections, said lower section having an integral surrounding wall, a rear portion of said wall being cut away at its upper half so as to permit lateral access to the interior of said lower section from the rear side of said flask, said upper section being adapted to be assembled with said lower section so as to form a substantially complete flask, and a depending flange on said upper section having the same dimensions as said cut away portion so as to nest therein and close the opening formed by said cut away portion.

4. A dental flask comprising a lower model investing section and closure means therefor, a surrounding wall integral with said lower section, an upper rear area of said wall being cut away substantially from side to side of the flask so as to form an opening and permit lateral access to the interior of said lower section, and a flange on said closure means for covering said opening when the flask is assembled.

5. A dental flask according to claim 4 wherein said closure means comprises an upper section formed with a surrounding wall of a depth sufficient to retain a mound of set plaster by embracing a portion thereof.

6. A dental flask for use in banking procedures comprising a lower model investing section, a covering section therefor, a surrounding wall integral with said lower section, a substantial portion of the rear area of said wall being cut away so as to form an opening and permit lateral access to the interior of said lower section, means on said covering section to enclose said opening when said flask is assembled, and means on said cover section to retain a set mound of plaster whereby said set mound ma serve as a plunger in said banking procedure.

NATHAN OPOTOW.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 926,583 Miller June 29, 1909 1,115,779 Brunton Nov. 3, 1914 2,188,415 Malsch Jan. 30, 1940 

